<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
    width: 200px;
    height: 400px;
    margin: 40px auto;
    background-color: #2b92d4;
    border-radius: 5px;
    box-shadow: 0 1px 2px rgba(0, 0, 0, .3);
    animation: breathe 2700ms ease-in-out infinite alternate;
}
@keyframes breathe {
    0% {
        opacity: .2;
        width: 200px;
        box-shadow: 0 1px 2px rgba(255, 255, 255, 0.1)
    }
    50% {
        opacity: .5;
        width: 400px;
        box-shadow: 0 1px 2px rgba(18, 190, 84, 0.76)
    }
    100% {
        opacity: 1;
        width: 200px;
        box-shadow: 0 1px 30px rgba(59, 255, 255, 1)
    }
}
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>